Fluid safety and arming system

ABSTRACT

A combined fluid safety and arming system for a gas propelled projectile including a normally opened arming circuit having a button-type detonator spaced from a fixed contact, a fluid motor for moving the button-type detonator, a high pressure chamber, a propellant gas inlet to the chamber, a fluid restrictor coupling the high pressure chamber with a fluid motor and a check valve positioned within the propellant gas inlet. A setback detent is operatively coupled to the fluid motor for restraining movement of the detent-type detonator in the absence of minimum launch acceleration.

United States Patent 1 Fisher [451 Aug. 7, 1973 1 FLUID SAFETY AND ARMING SYSTEM [75] Inventor: Evan D. Fisher, Chevy Chase, Md.

[73] Assignee: The United States of America as represented by the Secretary of the Army [22] Filed: Oct. 18, 1967 211 App]. No.: 677,844

[52] [1.8. CI 102/81, 102/76, lO2/49.6

[51] Int. Cl...... F421: 9/10, F42c 15/30, F42c 15/28 [58] Field of Search 102/7, 16, 78, 80, 102/81, 81.2, 86

[56] References Cited UNITED STATES PATENTS 1,850,196 3/1932 Bardsley 102/81 2,388,691 11/1945 Horan 102/78 2,831,431 4/1958 Stevenson et a1... 102/81 X 2,872,869 2/1959 Rasmussen 102/81 3,358,604 12/1967 Combourieux 102/76 3,362,333 H1968 Czajkowski et al. 102/81 Primary Examiner-Benjamin A. Borchelt Assistant ExaminerThomas H. Webb Attorney-Harry M. Saragovitz, Edward J. Kelly, Herbert Berl and G. L. Lett [57] ABSTRACT A combined fluid safety and arming system for a gas propelled projectile including a normally opened arming circuit having a button-type detonator spaced from a fixed contact, a fluid motor for moving the buttontype detonator, a high pressure chamber, a propellant gas inlet to the chamber, a fluid restrictor coupling the high pressure chamber with a fluid motor and a check valve positioned within the propellant gas inlet. A setback detent is operatively coupled to the fluid motor for restraining movement of the detent-type detonator in the absence of minimum launch acceleration.

10 Claims, 3 Drawing Figures FLUID SAFETY AND ARMIHNG SYSTEM Fluid operated detonators have been employed in conjunction with gas propelled projectiles wherein, subsequent to launch, either as a result of propellant gas pressure itself, or high pressure gas carried by the projectile, the pressurized gas is employed to move the detonator into position and to complete an electrical connection through the button contact carried thereby. In the known systems, where the gas pressure is obtained from a source of pressurized gas carried by the projectile itself, prior to actual firing of the projectile,

arming may inadvertently occur by faulty connection of the self contained pressurized gas to the fluid operated detonator. Further, the addition of pressurized fluid in container form greatly complicates the arming system and increases the cost of the same.

In an attempt to eliminate the need for a separate pressurized gas container attempts have been made to use the gas pressure caused by the projectile propellant means at the instant of firing to arm the shell or other projectile. While the known systems have obviously eliminated the requirement of a separate pressurized charge gas container, such known systems are deficient for two reasons. First, arming in response to fluid pressure must necessarily occur during the movement of the projectile within the bore of the firing device since, once the projectile leaves the firing device, it is obvious that any propellant gas produced during firing is lost to the projectile arming system. The arming of the projectile, with the projectile still within the weapon bore is exceedingly dangerous to the personnel firing the same. Further, as the projectile proceeds down the bore, there is a great variation in propellant gas pressure which may affect the actual time of arming reducing both arming reliability and timing.

It is therefore a primary object of this invention to provide an improved fluid arming system for a gas propelled projectile in which arming occurs at a precisely predetermined time subsequent to the projectile leaving the firing device.

It is a further object of this invention to provide a combined fluid safety and arming system which readily employs the projectile propellant gases and in which the time of arming subsequent to firing of the projectile remains constant regardless of fluctuations in propellant gas pressure.

It is a further object of this invention to provide an improved fluid safety and arming system for a gas propelled projectile in which the arming time for the pro jectile subsequent to firing maybe readily varied by minor changes to the system components.

It is a further object of this invention to provide an improved fluid safety and arming system for a gas propelled projectile in which the possibility of premature detonation prior to actual firing of the projectile is prohibited regardless of the inadvertent application of fluid pressure to the detonator when in projectile set down position.

Other objects of this invention will be pointed out in the following detailed description and claims and illustrated in the accompanying drawing which disclose, by way of example, the principle of this invention and the best mode which has been contemplated in applying the principle.

In the drawings:

FIG. l is a sectional elevation of a gas propelled projectile employing the fluid safety and arming system of the present invention.

FIG. 2 is a sectional, rear elevational view of the projectile shown in FIG. 1 taken about lines 2-2.

FIG. 3 is a plan view in section of the portion of the projectile shown in FIG. 2 taken about lines 3-3.

In general, the present invention is directed to an improved, combined fluid safety and arming system for a gas propelled projectile with the system comprising a detonator carried by the projectile and normally maintained in unarmed position, a fluid motor for moving the detonator, a high pressure chamber separated from the fluid motor, fluid coupling means coupling the high pressure chamber to the fluid motor and including a fluid restrictor, a propellant gas inlet to said high pressure chamber and a check valve positioned within said propellant gas inlet to allow a charge of high pressure propellant gas to enter the high pressure chamber and to be maintained therein after the projectile leaves the firing device whereupon, due to the restriction, there is a time delay between the firing of the projectile itself and the movement of the detonator into armed position in response to fluid motor operation. A set back detent is operatively coupled to the fluid motor for restraining movement of the same with the set back detent being released under minimum launch accelerations.

Referring to FIG. I of the drawing, there is shown a projectile which may comprise, for instance, a mortar shell, in the form of a slender elongated casing 12 including a plurality of fins 14 at the rear end in conventional fashion. The base mortar fuse assembly is indicated generally at 16 in a forward position within casing 112.

The present invention is directed to the fluid safety and arming system whih is activated by the propellant gas pressure generated when the mortar shell 10 is fired in a mortar tube (not shown). It is important only to note that upon firing of the mortar shell, there is sufficient hot propellant gas within the mortar tube to achieve arming of the mortar fuse 16 without the need for a completely separate source of pressurized gas in the form of a container or the like necessarily carried by the shell or casing 112.

The casing I2 is shown at the rear end as including an open ended, longitudinal bore l3 and a number of radial bores 20 connected thereto. Obviously, upon firing, bore R3 is filled with propellant gas at relatively high pressure. This propellant gas pressure acting on the rear surfaces of the shell causes it to move a direction from left to right through the mortar tube (not shown). The present fluid safety and arming system includes a high pressure chamber 22, formed by axial bore 211 which is spaced axially from bore 18 within shell casing 12 and separated therefrom by a threaded cylindrical member 24 having a somewhat smaller bore 216. Bore 26 forms an inlet passage to chamber 22. Bore 211 is counter-bored at 28 and again at 30. Counter bore 28 receives a piston member 32 which is held in position by a plug 33 threadably received within counter bore 30. The high pressure chamber 22 includes a ball check valve 36 which is maintain-ed against valve seat 33 by a coil spring 4M) which has its right hand end abutting the face of piston 32. Thus, with plug 34 in place and piston 32 acting on the right hand end of spring 40, the ball check valve 36 is maintained in closed position preventing direct fluid coupling between axial bore 18 and the high pressure gas chamber 22. However, upon firing, the high pressure gas moves through high pressure chamber inlet 26 unseating the ball check valve 36 and allowing high pressure gas to charge the chamber Forward of the high pressure chamber 22, there is provided a detonator slider assembly 42 which consists of a small piston 44 slidably carried within a vertically oriented bore 46 for movement in the direction of the bore axis in response to the application of fluid pressure to the upper face 48 of the piston. In this respect, the piston 44 includes an annular recess 50 spaced inwardly from face 48 which receives an O ring 52 for fluid sealing the detonator slider piston 44 with respect to bore 46.

As best seen in FIGS. 2 and 3, fluid pressure is delivered to face 48 of the detonator slider through an inclined passage 54 which is coupled at one end to bore 46 and at the other end to a chamber 56 formed by a second bore 58 and a threaded plug 60. The threaded plug 60 is axially movable with respect to bore 58 ,to vary the volume of chamber 56 and to therefore alter the timing characteristics of the arming system. Further, the high pressure chamber 22 is fluid coupled to chamber 56 by capillary tube means 62 comprising a plurality of turns of thin capillary tubing carried within a relatively large counter bore 64 intermediate of the fluid operated detonator assembly 42 and the high pressure chamber 22. One end 66 of the capillary tube is coupled to high pressure chamber 22 through a longitudinal passage 68 and a radial passage 70. The radial passage 70 is counter-bored at its outer end and threaded to receive a threaded control plug 74. Plug 74 includes a transverse slot 76 adapted to receive the end of a screwdriver (not shown). Therefore, the axial position of plug 74 may be adjusted to selectively control the rate volume of gas passing from the high pressure chamber 22 to the capillary tube assembly 62 and thence to the detonator assembly 42. Referring to FIG. 2, it is noted that the opposite end 78 of the capillary tube opens up into chamber 56.

While the particular type of electrical detonating system is not described in detail, it is noted that the system in all other respects is conventional and employs, as in conventional practices, the completion of an electrical circuit between the button 80 carried at the bottom of detonator slider piston 44 and a fixed contact or terminal 82 whichis positioned in the path of the button 80 at the bottom of bore 46.

The arming function for the base mortar fuse is achieved conventionally through an electronic module assembly including a source of voltage, indicated generally at 17 which surrounds a centrally positioned RDX lead charge 19. The electronic module achieves firing of charge'l9 in response to detonator slider button 80 contacting fixed electrical contact 82 which circuit includes module 17. In conventional fashion, the firing of the RDX lead charge causes the primary booster and shape charge 21 to be fired resulting in sequential firing of RDX booster 23 and the main charge located immediately in front thereof.

A separate set back detent indicated generally at 84 is provided to lock the slider piston 44 in place prior to firing. The configuration of the set back detent and its operation may be best seen by reference to FIG. 3. The set back detent comprises a spring biased piston 86 which is carried within a longitudinal bore 88 and normally forced into the position shown by a coil spring 90. Spring 90 is received within piston recess 92. The surface of piston 86 is dished at 94 throughout its periphery, the radius of curvature of the dished surface portion 94 being identical to radius of the slider piston 44. Thus, in the set down position, the detent is restrained by the bias offered by the coil spring 90 even if gas pressure is available to the face 48 of the detonator slider piston 44. However, upon firing of the shell, under minimum launch acceleration, the set back detent piston 86 will move in such a direction as to compress the spring 90 whereupon, the center of the dished portion 94 is planar aligned with the axis of the detonator slider piston 44 allowing high pressure gas acting on the piston face 48 to move the slider piston downwardly as shown in FIG. 1, past detent piston 86 to the point where button touches the fixed electrical terminal contact 82.

In operation, when the shell is fired in a mortar tube for instance, in normal fashion, propellant gas enters longitudinal bore 18 with a portion passing through chamber inlet 26, unseating the check valve 36 and causing a sufficient amount of high pressure propellant gas to be stored within chamber 22. The system is designed such that when the projectile exits from the mortar tube or firing device bore, the ball check valve, under the bias of spring 40, seats itself closing off the inlet passage 26 and maintaining a charge of high pressure propellant gas within chamber 22. This gas charge slowly bleeds through radial passage 70, longitudinal passage 68 and the multiple coils of the capillary tube means 62 and enters chamber 56 whereupon, it passes through the inclined passage 54 to the bore 46. Whereupon, it acts upon face 48 of the detonator slider piston 44. It is assumed that the 0 ring 52 or other means creates sufficient frictional resistance between the sliding piston 44 and bore 46 such that in the absence of high pressure fluid, the piston 44 will remain in the position shown in FIG. 1. Further, in response to minimum launch accelerations, the set back detent piston 86 will move from the position shown in FIG. 3, releasing the piston 44 and allowing it to be moved by fluid pressure to the point where contact button 80 meets fixed electrical contact 82. The detonator in armed position completes an appropriate electrical circuit, allowing the electronic module assembly 17 to ignite the RDX lead charge at 19. Adjustment may be readily made by means of the threaded plug 74 to vary the time rate of application of fluid pressure to the slider piston 44. Alternatively, more or less turns of capillary tube could be employed or the resistance of the capillary tube may be readily changed by increasing or decreasing the diameter of the capillary tube itself to vary the fluid resistance in the system. The combination of fluid restric- .tion and volume presents an equivalent RC delay time which is normally utilized to arm the fuse at 4:; 2 seconds after firing of the projectile itself. Chambers 22 and 56 provide the capacitive function to the RC network, while the capillary tube assembly 62 functions as the major fluid restriction. While the present fluid safety and arming system is employed in a projectile having an electronic or electrical detonatingsystem, the system has ready application to percussive or other types of detonators.

It is to be understood that the invention is not to be limited to the exact details of construction shown and described, for obvious modification will occur to a person skilled in the art.

What is claimed is:

l. A combined fluid and safety arming system for a gas propelled projectile, said system comprising: a normally inoperative detonator carried by said projectile, a fluid motor for moving said detonator into operative position, a high pressure chamber for receiving a propellant gas charge, a propellant gas inlet to said chamber, means for coupling said high pressure chamber to said fluid motor, means located between said high pressure chamber and said fluid coupling means for adjusting the rate of fluid flow to said fluid coupling means, and a check valve positioned within said propellant gas inlet.

2. The system as claimed in claim 7 wherein said restrictor comprises a capillary tube.

3. The system as claimed in claim 1 wherein said fluid motor comprises a piston slidable within a bore and means for frictionally retarding movement therein.

being in the form of a second piston carried within said second bore, and means for normally biasing said set back piston in blocking position relative to said fluid motor piston whereby, upon firing said set back detent piston moves from a blocking position to an unblocking position to allow pressurized fluid to move the detonator to activated position.

6. The system as claimed in claim 5 wherein said set back detent piston includes a circumferential recess having a radius of curvature on the order of the radius of said fluid motor piston, and said biasing means comprises a coil spring normally preventing planar alignment betwen the center of said set back detent piston and the axis of fluid motor piston.

7 The system as claimed in claim 1 wherein said fluid coupling comprises a fluid restrictor.

8. The system as claimed in claim 1 further comprising an intermediate chamber fluid coupled between said high pressure chamber and said fluid coupling means.

9. The system as claimed in claim 8 wherein the volume of said intermediate chamber is adjustable.

10. The system as claimed in claim 1 wherein said means for adjusting the rate of flow comprises a control plug located adjacent the outer boundary of said projectile, whereby said control plug is accessible from the exterior of the projectile. 

1. A combined fluid and safety arming system for a gas propelled projectile, said system comprising: a normally inoperative detonator carried by said projectile, a fluid motor for moving said detonator into operative position, a high pressure chamber for receiving a propellant gas charge, a propellant gas inlet to said chamber, means for coupling said high pressure chamber to said fluid motor, means located between said high pressure chamber and said fluid coupling means for adjusting the rate of fluid flow to said fluid coupling means, and a check valve positioned within said propellant gas inlet.
 2. The system as claimed in claim 7 wherein said restrictor comprises a capillary tube.
 3. The system as claimed in claim 1 wherein said fluid motor comprises a piston slidable within a bore and means for frictionally retarding movement therein.
 4. The system as claimed in claim 1 further including a set back detent, and means for operatively coupling said set back detent to said fluid motor for preventing movement of the same in the absence of projectile acceleration.
 5. The system as claimed in claim 4 wherein said fluid motor piston is positioned for movement within a first bore, a second bore at right angles to said first bore and partially intersecting the same, said set back detent being in the form of a second piston carried within said second bore, and means for normally biasing said set back piston in blocking position relative to said fluid motor piston whereby, upon firing said set back detent piston moves from a blocking position to an unblocking position to allow pressurized fluid to move the detonator to activated position.
 6. The system as claimed in claim 5 wherein said set back detent piston includes a circumferential recess having a radius of curvature on the order of the radius of said fluid motor piston, and said biasing means comprises a coil spring normally preventing planar alignment between the center of said set back detent piston and the axis of fluid motor piston.
 7. The system as claimed in claim 1 wherein said fluid coupling comprises a fluid restrictor.
 8. The system as claimed in claim 1 further comprising an intermediate chamber fluid coupled between said high pressure chamber and said fluid coupling means.
 9. The system as claimed in claim 8 wherein the volume of said intermediate chamber is adjustable.
 10. The system as claimed in claim 1 wherein said means for adjusting the rate of flow comprises a control plug located adjacent the outer boundary of said projectile, whereby said control plug is accessible from the exterior of the projectile. 